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HappyZappy
09-10-2010, 08:02 AM
Hi

I am using OpenGL version 3.0 and I want to test the transformfeedback feature.

I've write a app and doing it by
1) calling glTransformFeedback varyings() before vertex shader linking.
2) Binding trasform feedback buffer
3) calling beginquery with GL_TRANSFORM_FEEDBACK_PRIMITIVES_WRITTEN
4) glBeginTransformFeedback()
5) gl drawarrays
6) queryobject

At the end query object is returning a 0 primitives written.
If I query with the PRIMITIVE_GENERATED than it is giving me proper value but not sure why it is not retuning any primitive to TRANSFORM_FEEDBACK_BUFFER?
Moreover, I am able to see the display on screen. So data is in a framebuffer.

Could anyone tell me, how to get transform feedback buffer?

Thanks

YarUnderoaker
09-10-2010, 12:38 PM
You may use glEnable/glDisable(GL_RASTERIZER_DISCARD) to avoid drawing.
7) glEndTransformFeedback :)
Check XBO buffer for desirable data.

HappyZappy
09-15-2010, 06:51 AM
Thanks a lot for reply....

But could you also tell me how I can check the XBO data?

I am doing by -

GLfloat *data;
data = (GLfloat*) glMapBuffer(GL_TRANSFORM_FEEDBACK_BUFFER,GL_READ_O NLY);
tdkPrintf("data=====%d,%d,%d",data[0],data[1],data[2]);

I am getting very strange results like -
data=====1073741824,-1077528042,-2147483648

I am using the same example which is shown in a OpenGL red book on page - 724.

Could you please help me in reading the varying variables again.

Thanks.